Next-generation laser retroreflectors for precision tests of general relativity

Since 1969, Lunar Laser Ranging (LLR) to the Apollo Cube Corner Retroreflectors (CCRs) has supplied almost all significant tests of General Relativity (GR). When first installed in the 1970s, the Apollo CCRs geometry contributed only a negligible fraction of the ranging error budget. Today, because of lunar librations, this contribution dominates the error budget, limiting the precision of the experimental tests of gravitational theories. MoonLIGHT-2 (Moon Laser Instrumentation for General relativity High-accuracy Tests) is a new-generation LLR payload made of a single large CCR unaffected by librations in order to increase the precision of the GR tests compared to the Apollo CCRs. To optimize the MoonLIGHT-2 design and its lunar deployment we performed both experimental tests of MoonLIGHT-2 thermal properties in simulated space condition and GR test simulations using the Planetary Ephemeris Program (PEP) software, developed by the Center for Astrophysics (CfA). The experimental test shows the expected thermal properties and will provide useful to optimize the payload for the launch while the GR simulations suggest a significant improvement in GR test with the new CCRs and that the absence of a sunshade does not have a relevant impact on the precision of GR tests.